Variable height stairs for work platform

ABSTRACT

A variable height stairway, especially suitable for use with a height adjustable work platform. The stairway comprises step members forming a level base at the lowest position of the work platform and extending upwardly one at a time as the platform is raised in increments equal to the riser dimension of the stairway. The pitch of the stairway remains fixed at each elevated position.

o Umted States Patent 1 1111 3,757,894

Chamberlin 1 1 Sept. 11, 1973 [54] VARIABLE HEIGHT STAIRS FOR WORK 3,593,821 7/1971 Lister 182/115 PLATFORM 3,529,695 9/1970 Rowley.... 182/115 2,534,202 12/1950 McCall 182/195 Inventor: Virgil Chamberlin, Watsonville. 2,888,182 5/1959 Nixon 182/1 Calif.

[ Assigneel Lockheed F Corpflralion, Primary Exan r'r z er Reinal do P. Machado I Burbank, Callfziitofiy -Yeiichiro Imai and George C. Sullivan [22] Filed: June 5, 0172 [21] App]. No.: 259,907 57 CT A variable height stairway, especially suitable for use [52] US. Cl 182/106, 182/115, 11882515965, with a height adjustable work platform The Stairway Int Cl E06 comprises step members forming a level base at the l 5 Fie'ld 1 1 195 lowest position of the work platform and extending up- 8 wardly one at a time as the platform is raised in increments equal to the riser dimension of the stairway. The l References Cited pitch of the stairway remains fixed at each elevated position. UNITED STATES PATENTS 616,515 12/ 1898 Williams 182/1 8 Claims, 7 Drawing Figures .PATENIEUSEPI I I973 SHEEI 1 BF 3 FIG.

PAIEMED EPI 1 ms SHEEY 3 [If 3 VARIABLE HEIGHT STAIRS FOR WORK PLATFORM BACKGROUND OF THE INVENTION This invention relates to a variable height stairway and particularly to such a stairway when used with a height adjustable work platform.

DESCRIPTION OF THE PRIOR ART A common adjustable stairway is a folding stairway which is designed to be extended from a folded, or collapsed, position to one specific elevation. For example, such a stairway might be used in connection with a lift bridge over a canal. The bridge is elevated from its normal position across the banks of the canal to a higher set position. No intermediate positions are possible.

Other stairways using a parallelogram adjusting system can be adjusted to positions intermediate the collapsed and fully extended positions. However, the pitch, or the ratio between the riser and the tread dimensions, of these stairways varies at the different inf termediate positions. This pitch variation can present a safety hazard, and therefore these stairways are objectionable from the standpoint of industrial use.

SUMMARY OF THE INVENTION It is an object of the present invention toprovide a variable height stairway which can be adjusted to varying heights but at the same time maintains a fixed pitch.

It is also another object to provide a variable height stairway which will meet industrial safety codes.

These objects are achieved by a stairway which comprises a plurality of steps having a tread member and dual, spaced-apart, riser poles supporting the front portion of the tread member. The riser poles are approximately twice as long as the riser dimension of the stairway and are connected with a series of linkage members on each side of the steps. The linkage member consists of a horizontal link and two diagonal, generally parallel links connected to opposite ends of the horizontal link and extending in opposite directions. These individual links are connected to adjacent riser poles in such manner that, in the collapsed position of the stairway, the horizontal link is slidably attached with a ring to the first pole and fixedly attached with a collar to the second pole at approximately their mid-points. The upper end of the first, or upper, diagonal link is slidably attached with a ring to the top of the first pole and the lower end of the second, or lower, diagonal link is fixedly attached with a collar to the bottom of the second pole. The upper end of the first diagonal link also supports the rear portion of the tread member. At the mid-point of a pole, the collar of one horizontal link is superimposed on the ring of the adjacent horizontal link.

The end steps of the stairway are attached respectively to a fixed structure at ground level and to an elevatable work platform. The work platform is designed so that, in its lowest position, the present stairway is fully collapsed, forming a level base. The work platform is also designed to be elevatable in fixed height increments, an increment being equal to the riser dimension of the stairway. Thus, as the work platform is raised one increment, the attached end step is also raised, its riser poles passing through the rings of the adjacent linkage member. As the work platform is raised additional increments, the remaining steps are also raised, one by one, by the linkage arrangement described. At the various elevations of the work platform, the pitch of the stairway remains constant.

Other features and advantages of the present invention will become more apparent from the following detailed description of typical forms and application of the invention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view of the present stairway in conjunction with a work platform, the stairway being in its collapsed position, the handrail and part of the tread member being removed for clarity;

FIG. 2 is a similar view with the present stairway in its fully extended position;

FIG. 3 is a side elevational view of the present stairway in the collapsed position;

FIG. 4 is a side elevational view of the present stairway in its fully extended position; FIG. 5 is a front elevational view of the steps of FIG. 4, showing the riser portion of the tread member;

FIG. 6 is a fragmentary, sectional view along the line 6-6 of FIG. 5; and

FIG. 7 is a schematic diagram showing a pneumatic system for elevating the work platform.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIGS. 1 and 2, the present stairway 10 comprises end steps l2, l4 and intermediate steps 16, 18. Step 12 is attached to a fixed stairway extension 20 of a height adjustable work platform 22 (shown without the usual protective railing). Step 14 is attached to a base structure 24 fixed at ground level. Structure 24 can also be considered as an extension of the present stairway.

A typical step of the present stairway can be described in conjunction with step 16. Each step has a tread member 26 and dual riser poles 28 supporting the front portion of the tread member. The riser poles are approximately twice as long as the predetermined riser dimension of the stairway. As shown in FIGS. 3 and 4, the riser poles are serially connected by a linkage member, generally designated as 30, comprising a horizontal link 32, an upper diagonal link 34, and a lower diagonal link 36. The diagonal links are connected to opposite ends of link 32, as shown. Link 32 is attached to two adjacent poles 28 at approximately their mid-points. The first pole is additionally designated here as 2811 and the second as 28b for greater clarity. Link 32 is slidably attached to pole 28a with a ring 38 and fixedly attached to pole 28b with a collar 40. The upper end of diagonal link 34 is also slidably attached to the top of pole 28a with a ring 42. The lower end of diagonal link 36 is fixedly attached to the bottom of pole 28b with a collar 44. The terms ring and collar," as used herein, both refer to annular members, but the term ring designates a member having a larger inside diameter than the pole outside diameter so that the pole can slide freely inside the member and the term collar refers to a member that is held rigid with respect to the pole, as by welding.

Work platform 22 has telescopically adjustable support legs 46, 48 (FIGS. 1 and 2). As shown schematically in FIG. 7, these legs may be raised and lowered by introducing pressurized air from main air line 50 into the upper cylinder portions 52 of the legs. (Only one of the legs is shown in full in FIG. 7, but the other legs have the same construction.) An annular seal element 54 at the top of the lower column 56 of the legs provides the necessary sealing. To take into account the difference in weights supported by the legs 46 and 48, separate branch air lines 58, 60 with separate hoist valves 62, 64 and speed control valves 63, 65 may be provided for each set of legs. When the desired elevation of work platform 22 is reached, pins 66 are inserted into the appropriate pinhole 68 in column 56 to hold the legs at the desired position (FIG. 2). The pinholes 68 are separated by a distance equal to the riser dimension of stairway 10.

As the work platform 22 is raised, the linkage arrangement previously described causes the individual steps in the stairway to be also raised one by one from the collapsed position shown in FIG. 3. Thus, when the platform is raised one height increment, as measured by pinholes 68, the lift forces are transmitted to step 12 causing poles 28a to rise through the rings 38, 42 of the adjacent linkage member. When the platform is raised another height increment, the lift forces are now transmitted through the adjacent linkage mem ber causing step 16 to be lifted. This process is continued until the entire stairway is extended as shown in FIG. 4.

As a safety measure, the present stairway is provided with a guardrail, generally shown as 70, which comprises posts 72, 74, 76 mounted respectively on steps l2, l8 and base structure 24 and telescopically adjustable handrail segments 78, 80 pivotally mounted on posts 72, 74, 76. The telescoping construction and the pivotal mounts allow for total or partial extension of stairway 10.

Also, as another safety feature, the tread members 24 are provided with depending riser portions 82 with openings 84 to allow for clearance of the linkage member 30 (FIG. 5). Riser portions 82 prevent accidents which might otherwise occur because of openings in the stairway.

The combination of the present stairway with a work platform, as previously described, provides a work stand which has been found to be particularly useful in the manufacture and servicing of large aircraft. The stand can be placed on caster wheels and moved to various locations around the aircraft. At a particular location, the work platform can be adjusted to a height which would be most convenient for the particular work being done on the aircraft. The fixed pitch on the stairway and the other safety features mentioned enable the workstand to meet industrial safety regulations.

Although the present stairway has been described and illustrated with reference to a work platform, it will be understood that the invention is not so limited and that various changes may be made therein without departing from the spirit of the invention or the scope of the appended claims.

I claim:

I. A stairway adjustable in height from a level position to a plurality of elevated positions, said stairway comprising: a plurality of steps, each step having a tread member and dual, spaced-apart riser poles extending below and supporting the forward portion of the tread member; a series of linkage means joining the riser poles on each side of the steps and supporting the rear portion of the tread members; said linkage means being slidably attached to a pole in one step whereby said step can be moved relative to an adjacent step and said linkage means being fixedly attached to a pole in an adjacent step whereby the movement of the one step can be transmitted to move the adjacent step.

2. A stairway according to claim I, wherein the linkage means in the level position of the stairway comprises: a horizontal link joining adjacent riser poles at approximately their mid-points, said link being slidably attached with a ring to the first of said adjacent poles and fixedly attached with a collar to the second of said poles; a first diagonal link connected to the horizontal link adjacent the second pole and slidably attached with a ring to the top of the first pole; a second diagonal link connected to the horizontal link adjacent the first pole and fixedly attached with a collar to the bottom of the second pole.

3. A stairway according to claim 2, wherein the collar on a horizontal link is superimposed on the ring on the adjacent horizontal link.

4. A stairway according to claim 2, wherein the tread member comprises a tread plate with a depending riser portion configured to clear the riser poles.

5. A stairway according to claim 3, including a guardrail having posts on one side of the steps and horizontal, telescoping handrail segments pivotally mounted on the posts.

6. A workstand comprising: a work platform having telescopically adjustable legs, said legs being adjustable in height in predetermined increments; means for adjusting the height of the legs; and a height adjustable stairway attached to the work platform, said stairway comprising: a plurality of steps, each step having a tread member and dual, spaced-apart riser poles supporting the forward portion of the tread members; a series of linkage members joining the poles on each side of the steps and supporting the rear portion of the tread members; said linkage means being slidably attached to a pole in one step and fixedly attached to a pole in an adjacent step whereby adjacent steps can be moved relative to each other in an amount equal to the predetermined height increment of the platform legs.

7. A workstand according to claim 6, wherein the predetermined height increment is equal to the riser dimension of said stairway.

8. A workstand according to claim 6, wherein the linkage members in the level position of the stairway comprise: a horizontal link joining adjacent riser poles at approximately their mid-points, said link being slidably attached with a ring to the first of said adjacent poles and fixedly attached with a collar to the second of said poles; a first diagonal link connected to the horizontal link adjacent the second pole and slidably attached with a ring to the top of the first pole; a second diagonal link connected to the horizontal link adjacent the first pole and fixedly attached with a collar to the bottom of the second pole. 

1. A stairway adjustable in height from a level position to a plurality of elevated positions, said stairway comprising: a plurality of steps, each step having a tread member and dual, spaced-apart riser poles extending below and supporting the forward portion of the tread member; a series of linkage means joining the riser poles on each side of the steps and supporting the rear portion of the tread members; said linkage means being slidably attached to a pole in one step whereby said step can be moved relative to an adjacent step and said linkage means being fixedly attached to a pole in an adjacent step whereby the movement of the one step can be transmitted to move the adjacent step.
 2. A stairway according to claim 1, wherein the linkage means in the level position of the stairway comprises: a horizontal link joining adjacent riser poles at approximately their mid-points, said link being slidably attached with a ring to the first of said adjacent poles and fixedly attached with a collar to the second of said poles; a first diagonal link connected to the horizontal link adjacent the second pole and slidably attached with a ring to the top of the first pole; a second diagonal link connected to the horizontal link adjacent the first pole and fixedly attached with a collar to the bottom of the second pole.
 3. A stairway according to claim 2, wherein the collar on a horizontal link is superimposed on the ring on the adjacent horizontal link.
 4. A stairway according to claIm 2, wherein the tread member comprises a tread plate with a depending riser portion configured to clear the riser poles.
 5. A stairway according to claim 3, including a guardrail having posts on one side of the steps and horizontal, telescoping handrail segments pivotally mounted on the posts.
 6. A workstand comprising: a work platform having telescopically adjustable legs, said legs being adjustable in height in predetermined increments; means for adjusting the height of the legs; and a height adjustable stairway attached to the work platform, said stairway comprising: a plurality of steps, each step having a tread member and dual, spaced-apart riser poles supporting the forward portion of the tread members; a series of linkage members joining the poles on each side of the steps and supporting the rear portion of the tread members; said linkage means being slidably attached to a pole in one step and fixedly attached to a pole in an adjacent step whereby adjacent steps can be moved relative to each other in an amount equal to the predetermined height increment of the platform legs.
 7. A workstand according to claim 6, wherein the predetermined height increment is equal to the riser dimension of said stairway.
 8. A workstand according to claim 6, wherein the linkage members in the level position of the stairway comprise: a horizontal link joining adjacent riser poles at approximately their mid-points, said link being slidably attached with a ring to the first of said adjacent poles and fixedly attached with a collar to the second of said poles; a first diagonal link connected to the horizontal link adjacent the second pole and slidably attached with a ring to the top of the first pole; a second diagonal link connected to the horizontal link adjacent the first pole and fixedly attached with a collar to the bottom of the second pole. 